Cleantech innovations. IIT Guwahati researchers design "smart windows" to cut carbon emissions

Climate control of windows and glass facades of structures can be easier and cheaper with a team of researchers at the Indian Institute of Technology (IIT) Guwahati developing a nanocoating that can regulate heat and light passing through such structures in response to an applied voltage.

.Buildings account for nearly 39 per cent of the energy-related carbon dioxide emissions annually. The primary consumption of energy in buildings is by climate control systems, in which energy-consuming devices are used to maintain comfortable indoor temperatures and brightness. To meet the goals of the Paris Climate Agreement, a building energy intensity will have to improve by 30 per cent by 2030.

However, achieving such a target is made easier by innovation by Debabrata Sikdar, an assistant professor at IIT's Department of Electronics and Electrical Engineering, and his research student Ashish Kumar Chowdhary. They have designed a smart window material that can effectively control the amount of heat and light passing through these windows in response to an applied voltage. Such materials can help develop efficient automatic climate control systems in buildings, the scientists claimed. Their work was recently published in the journal Solar Energy Materials and Solar Cells .

More importantly, the coating they have developed can be applied on existing windows as an adhesive film. The material required for this would cost as little as Rs 1-2 per square metre, the scientists said.

“ There has been increased attention to sustainable architectural designs for better light and heat management in buildings in recent years, and deploying smart windows is the first step for such structures,” Sikdar said in a statement.

Designing

Conventionally, window designs are static, that is, they are pre-designed for specific climatic conditions. On the other hand, the emergent smart windows can dynamically adjust the amount of light and heat radiation entering a building in response to external stimuli, thus conserving the building’s energy.

The design of smart windows that are tuneable for all-weather conditions is challenging. The IIT Guwahati team has designed smart window ‘glasses’ using noble metals and their relatively inexpensive alternatives that can dynamically control the intensity of transmitted solar radiation, depending upon the weather/climate condition.

“We have proposed an electro-tuneable glass made of two ultra-thin metal layers sandwiching an electro-optic polymer whose refractive index can be changed by applying a small voltage, which allows filtering of visible and infrared radiation,” explained Chowdhary .

The researchers used this design to perform simulation studies to understand the light and heat transmission properties in response to the applied voltage. They initially considered gold and silver as the metal layers but later tested their model with cheaper alternatives such as copper, and transparent semiconductor such as indium tin oxide.

These smart glasses can find applications for efficient automatic climate control in vehicles, locomotives, airplanes and greenhouses of the future. The smart glass material proposed by the IIT Guwahati team can easily be fabricated using existing state-of-the-art nanoscale fabrication methods such as e-beam evaporation and graphoepitaxy techniques.

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